It is well known that the former pressure swing gas separation technology usually has the following disadvantage whether obtaining the product from the strongly adsorbed phase (e.g. this technology has been employed to produce pure carbon dioxide from the strongly adsorbed phase.) or obtaining the product from the weakly adsorbed phase (e.g. this technology has been employed to produce pure hydrogen from the weakly adsorbed phase) or obtaining the product from both of the weakly adsorbed and the strongly adsorbed phase (e.g. this technology has been also applied in the production of carbamide from synthetic ammonia shift gas by removing carbon). These kinds of the patents include CN 1235862A, CN1248482A, CN1357404A CN1347747A, CN1342509A, CN1334135A and CN1334136A, etc. However it has been seen that the conventional pressure-swing gas adsorption technology possesses significant disadvantages in terms of the lost of the effective gases and the high operation cost, etc. The present invention involves improvements based on the pressure-swing adsorption gas separation technology mentioned above, namely, in this invention there is almost no lost of the effective gas, and in addition, this invention does not need the complicated vacuum facilities under suitable adsorption pressure. Therefore, the cost of the equipment and the power consumption will be remarkably reduced.